Moisture measuring system



Jan 15, 1963 A. L. PETITJEAN MOISTURE MEASURING SYSTEM Filed Jan. 19, 1960 wwf/'W ATTORNEY fk-through the use of relatively inexpensive measuring in- United States Patent O 3,073,153 MHSTURE MEASURING SYSTEM Alger L. Petitjean, 13318 8th Ave. NW., Seattle 77, Wash. Filed Jan. 19, 1960, Ser. No. 3,324 Claims. (Cl. 73--73) This invention relates to the measurement control of a characteristic of continuously moving sheet material. More particularly, this invention relates to the measurement and control of moisture in a machine for producing paper, at locations wherein the paper has a relatively high moisture content, and especially to the control of the moisture content in the production of extensible paper by the Clupak process.

In the manufacture of paper, fibrous material is deposited upon a rapidly moving screen from a pulp slurry. This very wet sheet is then passed through many drying stages to ultimately produce the dried continuous sheet of paper which is wound upon a reel. Within the sequence of operations between the initial dryer and the wind up reel, the paper is frequently subjected to additional processing steps for various purposes. For optimum results in these various additional steps it is necessary to have the continuously moving paper sheet at a relatively high but accurately controlled moisture content.

As a particular example wherein it is necessary to control the moisture content of a continuously moving sheet, may be mentioned the recently developed Clupak process for making extensible paper. The performance of this process is dependent greatly upon the moisture content of the paper entering the extensible unit. Prior to the present invention, there was no known Way of continuously determining the moisture content of a continuously moving paper sheet having a relatively high moisture content. In such paper the electrical conductivity is substantially increased. Presently existing instruments for determining the moisture content of a continuously moving paper sheet are therefore limited to applications wherein the paper sheet has a relatively low moisture content only. Since the paper in the Clupak process has a high moisture content, control of the extensible paper process could not be based upon continuous measurements of the wet paper entering the extensible unit and the operation of the extensible unit could not be as accurately controlled as desired.

Accordingly, an object of the present invention is to provide new and improved methods and apparatus whereby accurate measurement and control of moisture in a rapidly moving continuous sheet may be determined rapidly and continuously.

A second object of this invention is to measure and control such moisture content Without the necessity of removing samples from the continuous sheet, destroying portions of the sheet or interrupting the continuity of the process.

It is a further object of this invention to determine the moisture content of the continuously moving sheet struments and computers.

With the above objects in view, the present invention mainly consists of apparatus for measuring the moisture content of continuously moving sheet material prior to the drying thereof and including means responsive to the basis weight of the sheet material for producing a first output signal which is a function of the basis weight. Means are also provided which are responsive to the bone dry material content per unit area present in the sheet material after drying of the same for producing a second out'- put signal which is a function of this bone dry material content per unit area. Finally, means are provided which appended claims.

Patented Jan. 15, 1963 ICC are responsive to the first and second output signals for producing a third output signal which is a function of the moisture content of the sheet material before the same is dried.

The novel features which are considered as characteristic for the invention are set forth in particular in the The invention, itself, however, both as to its construction and its method of operation, together with additional objects and `advantages thereof, will be best understood from the following description when read in connection with the accompanying drawing, the sole FIGURE of which is a schematic diagram of a specific embodiment.

Referring to the drawing, there 'is shown schematically the instrumentation applied for the measurement and control of the Clupak process for making extensible paper.

The apparatus for performing the basic Clupak process is shown on the bottom of this ligure and comprises. generally a dryer section 11, extensible unit 12, nal dryer 13, and wind-up reel 14. The extensible unit 12 comprises a dryer drum 16, a nip roll 17, carrier rolls 18 and 19, and a thick endless rubber blanket 20 carried by rolls 17, 18, Iand 19.

'I'he nip roll 17 is spaced from dryer drum 16 by a distance which is vless than the thickness of endless rubber blanket 20. Relatively moist paper 22 (having about 30- 35% moisture content) is fed into the nip between nip roll 17 and dryer drum 16 along with theendless rubber blanket 20. The compression of the endless rubber blanket 20 in this nip causes paper 22 to acquire a microscopic crimp which reduces the length of sheet 22 in the direction of movement of the sheet. The crimped sheet 23 leaving the extensible unit is then dried in the nal dryer section 13 to the desired moisture content for storing and ultimate use.

The present invention is particularly well adapted for the control of the above described basic process and accordingly this process -will be used for illustrating the invention.

In accordance with the present invention, several meas'- uring instruments are positioned along the path of movement of the paper sheet through the paper making machine. Positioned adjacent the relatively wet paper sheet 22 before the extensible unit 12 area noncontact measuring gauge 26 of the nuclear or X-ray type for measuring the basis weight of sheet 22, and a linear speed sensing instrument 27 for sensing the linear speed of sheet 22.

Positioned adjacent the finally dried extensible paper sheet 24 are non-content measuring gauge 31 of the nuclear or X-ray type for measuring the basis weight of sheet 24; linear speed sensing instrument 32 for sensing the linear speed of sheet 24; and moisture sensing instrument 33 for sensing the moisture content of the relatively dry extensible paper sheet 24. f

As examples of specific instruments which may be used in the above system, basis weight sensing instruments 26 and 31 may be the Betameten moisture sensing instrumen-t 33 may be the Aquatel, and linear speed sensing instruments 27 and 32 may be Draw Speed Gauges, yall of which instruments are made and sold by the Curtiss- Wright Corporation under the foregoing trade names.

The outputs of these various sensing'instruments are used by the indicating and/ or control instruments andl computers in the following manner: Moisture sensing instrument 33 produces an output sig-v nal which is a function of the percent moisture Mf in j the extensible paper sheet 24 and transmits it by means 41 also produces a final dryer control signal which it emits on conductor l131 and which is used to control the operation of final dryer 13 to maintain the value of the moisture content in the finally dried extensible paper sheet 24 within the preselected limits. Recorder 41 also provides a second output signal which is a function of Mg and applies the same on conductor 411 to bone dry fiber computer 43.

Non-contact iinal basis Weight measuring gauge 31 produces anroutput signal which is a function of the basis weight Bf of sheet 24 and transmits it through conductor 311 to final basis weight recorder 42. Recorder 42 responds to this output signal by producing an indication of the final basis weight of sheet 24. Recorder 42 also provides an output signal which is applied on conductor 421 to bone dry fiber computer 43. f

The bone dry iiber computer 43 utilizes the output signals from recorders 41 and 42, to produce output signals which are functions of the amount of bone dry iiber per unit area of the extensible paper sheet 24. This computer operates according to the following formula:

Wherein:

Pf=The weight ofv bone dry fiber per unit area of exten- 'sible paperA sheet 24;

B1=The basis weight (or total weight per unit area) of vsheet 24; and

Mf=The percent moisture in extensible paper sheet 24.

, Bone dry fiber computer 43 produces an output signal, Which is proportional to Pt, on output conductor 431 and applies the signal to final fiber weight recorder 44. Recorder 44 produces an indication of the amount of bone dry fiber per unit area contained in extensible paper sheet 24.

Computer `43 `also produces a paper making control signal on output conductor 432 which is used for controlling the operation of the paper making machine (not shown) producing paper sheet 22. This control mechanism and the paper making machine are not illustrated in order to avoid unnecessarily complicating the drawing.

Computer 43 also produces an output signal on conductor 433 which is a function of the bone dry fiber per unit area and applies the vsame to moisture computer 46.

The linear speed sensing instruments 27 and 32 arranged before and after the extensible unit 12 `produce output signals on conductors 271 and 321, respectively, which are functions of the linear speeds Si and Sf, respectively, of relatively moist paper sheet 22 and extensible paper sheet 24, respectively. These output signals are both applied to a draw computer 47, computer 47 produces an output signal on Vconductor 471 which is a function of the draw coeicient D=S1/Sf. This output signal is transmitted through conductor 471 .to moisture computer 46. Draw computer l47 may also produce an indication of the draw coefficient D for display or control purposes if desired.

Non-contact intermediate basis weight measuring gauge Y26 arranged vafter dryer 11 produces an output signal which is a function of the basis weight B, of relatively moist sheet 22 and transmits it through conductor 261 to intermediate basis weight recorder 49. The recorder 49 uses this signal (which is a function of B1) to produce an indication of the intermediate basis Weight of sheet 22. Recorder 49 also transmits an output signal through conductor 491 to moisture computer 46'. This output signal is also a function of the basis weight Bi. l

The moisture computer 46 receives signals from bone dry fiber computer 43, draw computer 47, and non-contact measuring gauge 26 through conductors 433, 471, 491, respectively, and uses them to compute the water-to-fber ratio of continuously moving sheet 22 according to the following formula:

init-M Pi- Pr Wherein:

1l=The Water-to-ber ratio of relatively moist sheet Moisture computer 46 produces an output signal, which is a function of Wi/Pi, on conductor 461 and is conducted to intermediate water/ber ratio recorder controller 4S. Recorder-controller 48 produces an indication of the ratio of water-to-ber in the continuously moving paper sheet 22. Intermediate water/fiber ratio recorder-controller `48 also produces on conductor 481 a dryer control signal for controlling the operation of dryer 11 to maintain the value of the moisture content in sheet 22 Within the preselected desired limits.

In operation as the paper 22 passes from the dryer 11 to the extensible unit 12 the basis weight of the paper is recorded in the moisture computer 46 by means of the gauge 2-6 and recorder 49. The linear speed of the paper 22 is recorded in the draw computer 47 by means of linear speed measuring instrument 27.

After the extensible paper 24 emerges from the final dryer 13, its linear speed is also recorded in the draw computer 47 by means of the linear speed sensing instrument 32. The draw computer 47 produces an output signal which is a function of the draw speed coefficient and applies the same to the moisture computer 56. Similarly, the basis Weight of the paper 24 after the iinal drying position is recorded in the bone dry fiber computer 43 by means of the gauge 31 and the final basis weight recorder 42. Also recorded in the computer 43 is the moisture of the paper 24, by means of the moisture sensing instrument 33 and the tinal moisture recorder 41.

As indicated hereinabove computer 43 provides an output signal Pf which is a function of the weight of the bone dry iber per unit area of extensible paper sheet 24. This signal is applied to and utilized in the moisture computer 46 in conjunction with `the draw coeflicient and the intermediate basis Weight of the paper 22 previously recorded therein. The resultant signal available from the computer 46 in accordance with Equation 2 is a function of the water-to-tber ratio of the sheet 22.

This information is displayed on the recorder 48 sothat an operator may vary the process controls manually to bring the water-to-fiber ratio within the preselected limits thereof. The signal may also be used for automatic control of the paper processing equipment if such automatic control equipment is utilized. The water-to-ber ratio of course is indicative of the quality and content ofl the paper being utilized.

This invention has been described in a particular embodiment particularly adaptable for producing, display- Y ing, and controlling a maximum of the variables in the Clupak process for making extensible paper. If desired, however, the various display units may be omitted and the sensing instruments and computers used solely for control purposes. Alternatively the automatic control functions may be omitted and the various instruments used solely to produce continuous displays of the magnitudes of the variables. Also depending upon the amount of information and control desired, various of the instruments 4l, 42, 44, l49 and 48 may be omitted or some of their functions omitted or simplified, the only essential soreness functions being to transmit the outputs of the various sensing elements to the computers 43 and 46.

While the invention has been `described specifically as applied to the Clupak process for preparing extensi- -ble paper, where it is especially useful, this invention for determining the moisture content of a continuous sheet of relatively moist material is useful in many other applications, and may be readily adapted thereto. For example, where the after treatment of the relatively moist sheet (which after treatment includes a final drying) does not produce any change in the dimensions of the continuous sheet, the `draw computer 47 and the associated sensing instruments 27 and 32 may 'be omitted since the draw coefficient D would then be equal to a constant 1.

While the invention has been illustrated and described as embodied in a certain particular apparatus, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention as defined in the claims.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should be and are intended to be comprehended within the meaning and range of equivalents of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. In apparatus for measuing the moisture content of continuously moving sheet material prior to the drying thereof, in combination, means responsive to the basis weight of the sheet material before drying for producing a first output signal which is a function of said basis weight; means for producing a second output signal which is a function of the lineal speed of said continuously moving sheet material before drying; means for producing a third output signal which is a function of said lineal speed after the drying of said sheet material; means responsive to said second and third output signals for producing a fourth output signal which is a function of the draw coefficient of said continuously moving sheet; means responsive to the bone dry material content per unit area present in said sheet material after drying of the same and for producing a fth output signal which is a function of said bone dry material; and means responsive to said fourth and fifth output signals for producing a sixth output signal which is a function of the moisture content of said sheet material before the same is dried.

2. Apparatus as claimed in claim 1 wherein said means for producing said fifth output signal is a bone dry fiber computer which includes means for measuring the moisture content and the basis weight of said sheet material after the same is dried.

3. In apparatus for measuring the moisture content of a relatively moist, continuously moving, continuous sheet which is subsequently dried, comprising, in combination; first means for producing an output signal which is a function of the amount of bone dry material per unit area of the subsequently dried sheet; second means for producing an output signal which is a function of the basis weight of the relatively moist sheet prior to the subsequent drying; third means for producing an output signal which is a function of the ratio of the speed of movement of said continuously moving continuous sheet at the location of said second means to the speed at said first means; and fourth means for producing an output signal which is a function of the output signals from said first means, said second means, and said third means, thereby producing an output signal which is a function of the moisture content of the relatively moist sheet.

4. In apparatus for making extensible paper and including an initial dryer, an extensible unit, a final dryer, and a wind-up reel: improved moisture measurement means, comprising means for producing a first signal which is a function of the moisture content per unit area of said paper after passing through said final dryer; means for producing a second signal which is a function of the basis weight per unit area of said paper after passing through said final dryer; computer means responsive to said first and second signals for producing a third signal which is a function of the bone dry weight pei unit area of said paper; means for producing a signal which is a function `of the basis Weight per unit area of the paper sheet after said sheet paseses through said initial dryer; and moisture computer means responsive to said third and fourth signals for producing a fifth signal which is aV function of the moisture content per unit area of the paper after passing through the initial dryer and before passing through said final dryer.

5. Apparatus for measuring the moisture' content of continuously moving sheet material prior to the drying thereof which comprises: means responsive to the basis weight of the sheet material before drying for producing a first output signal which is a function of said basis Weight; means responsive to the basis weight of said sheet material after drying for producing a second output signal which is a function of said basis weight after drying; means responsive to the moisture content of said sheet material after drying for producing a third signal which is a function of the moisture content of said sheet material after drying; means responsive to said second and third signals for producing a fourth signal which is a function of the bone dry weight of said material; and means responsive to said first and fourth signals for producing a fifth output signal which is a function of the moisture content of said sheet material before drying.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,296 Carpenter Aug. 21. 1934 2,937,280 Gilman May 17, 1960 2,948,850 Ederer Aug. 9, 1960 2,951,007 Lippke Aug. 30, 1960 

1. IN APPARATUS FOR MEASURING THE MOISTURE CONTENT OF CONTINUOUSLY MOVING SHEET MATERIAL PRIOR TO THE DRYING THEREOF, IN COMBINATION, MEANS RESPONSIVE TO THE BASIS WEIGHT OF THE SHEET MATERIAL BEFORE DRYING FOR PRODUCING A FIRST OUTPUT SIGNAL WHICH IS A FUNCTION OF SAID BASIS WEIGHT; MEANS FOR PRODUCING A SECOND OUTPUT SIGNAL WHICH IS A FUNCTION OF THE LINEAL SPEED OF SAID CONTINOUSLY MOVING SHEET MATERIAL BEFORE DRYING; MEANS FOR PRODUCING A THIRD OUTPUT SIGNAL WHICH IS A FUNCTION OF SAID LINEAL SPEED AFTER THE DRYING OF SAID SHEET MATERIAL; MEANS RESPONSIVE TO SAID SECOND AND THIRD OUTPUT SIGNALS FOR PRODUCING A FOURTH OUTPUT SIGNAL WHICH IS A FUNCTION OF THE DRAW COEFFICIENT OF SAID CONTINUOUSLY MOVING SHEET; MEANS RESPONSIVE TO THE BONE DRY MATERIAL CONTENT PER UNIT AREA PRESENT IN SAID SHEET MATERIAL AFTER DRYING OF THE SAME AND FOR PRODUCING A FIFTH OUTPUT SIGNAL WHICH IS A FUNCTION OF SAID BONE DRY MATERIAL; AND MEANS RESPONSIVE TO SAID FOURTH AND FIFTH OUTPUT SIGNALS FOR PRODUCING A SIXTH OUTPUT SIGNAL WHICH IS A FUNCTION OF THE MOISTURE CONTENT OF SAID SHEET MATERIAL BEFORE THE SAME IS DRIED. 